Reservoir well production and testing involves drilling subsurface formations and monitoring various subsurface formation parameters. Drilling and monitoring often involves using downhole tools having electrical, mechanical and/or hydraulic devices. Pump systems are utilized to power downhole tools using hydraulic power. Such pump systems may be configured to draw hydraulic fluid from a reservoir and pump the fluid at a particular pressure and flow rate. The pump systems can be controlled to vary output pressures and/or flow rates to meet the needs of particular applications. In some example implementations, pump systems may also be utilized to draw and pump formation fluid from subsurface formations. A downhole string (e.g., a drill string, a wireline string, etc.) may include one or more pump systems depending on the operations to be performed using the downhole string.